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I usually hit the trail in October, and carry two space blankets (they weigh next to nothing). One goes in the undercover. The other one is for unexpected temperature drops. I've slept down to 34 degrees(F), and that's a bit chilly. I run the second space blanket in a diamond shape above the ridgeline and below the mosquito netting. I've found I have to fold back the part that's directly over my face, or condensation occurs from my breath. The rest of me is as warm as a burrito in the microwave. It does get a little noisy, as the space blankets seem to get more 'crinkly' as the temperature goes down.

So your thought is that it wouldn't have mattered if it were a space blanket or a trash bag?

Ive just tried one night at -2°C with the space blanket replaced by a panel of PU coated polyester tent fabric. There was no significant difference in warmth or condensation management, but it was substantially less noisy!

Ive just tried one night at -2°C with the space blanket replaced by a panel of PU coated polyester tent fabric. There was no significant difference in warmth or condensation management, but it was substantially less noisy!

Originally Posted by Owl

Interesting. Wonder if just using a layer of 3mil contractor bag cut open to fit over the underpad would have the same effect?

It is quite possible. I have been asking for years: is the obvious ( to me and at least a few others) benefit of adding the sp.blanket to the HHSS due to radiant block, due to some radiant added to a full VB effect, or is it just all VB effect? No one has given me a definite answer - or I have forgot if they did - and I have never taken the time to try and rig up some "controlled" comparisons. ( probably because this would be tricky trying to account for all of the variables. )

Here is the problem of trying to test: look at tdickenson's test. Apparently, he was warm enough at just below freezing. Right about where I find a basic system good for for me. Has he been any lower than that when using the SB? Certainly some here have. If he can go lower, is it due to adding some radiant block to the VB effect? But for that matter, could he have gone lower with the PU coated polyester tent fabric, even as low as with the SB?

If you can get say 15F added with a plan VB, can you get maybe 17 or 20 with a radiant + VB? Does any one know? I suspect that most of the effect is VB, but is it all of the effect?

I think if there is any benefit from any radiant block, it is small, but I'm just guessing. It would be hard to determine from back yard tests if your VB got you a 15F boost but the SB got you a 17F boost. It could be found out in some sort of controlled lab test, but a small difference would be hard for me to detect. And a test would have to be side by side on the same day with all other insulation and materials identical. Even then, it would be tough to tell- by feel - a small dif. Maybe if some sort of thermometer was used, taped to your back and transmitting to a separate unit?

Being an on and off VB user for years, it "seems" to me that I notice the warmth boost much more quickly when I add an SB over the HH pad than I do when just using VB clothing. But that could be in my head, and is certainly not an A to B comparison.

Plus, Dirtwheels recently got a warm at 23 night out of a 45F UQ, an extra 22F. That is starting to push the most optimistic claims I normally see for VBs ( an extra 15 to 20?). But it could just be the UQ is good for several more degrees than rated, at least for Dirtwheels.

How about testing with- if there is such a thing - a breathable sb? If it really was quite breathable, and if you still got a significant warmth boost, then I suppose that would mean that radiant block counts for something?

Regardless, interesting discussion!

For I consider that the sufferings of this present time are not worthy to be compared with the glory that is to be revealed to us....that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. For we know that the whole creation groans and suffers the pains of childbirth together until now.
Romans 8:18,21-22

How about testing with- if there is such a thing - a breathable sb? If it really was quite breathable, and if you still got a significant warmth boost, then I suppose that would mean that radiant block counts for something?

Regardless, interesting discussion!

I can't imagine that there is a breathable SB out there...although tyvek has been considred a "breathable vapor barrier".

And the only way I can imagine trying to actually test what works best would be to spend time in one setup, break down and reset for the other condition, and then spend the same time in the new setup...assuming the rest of the test conditions remain consistent throughout your test period.

I can't vouch for much other than again I used the HHSS, with SB, this past weekend in weather down around 30 deg and pretty humid out both nights. Inside the hammock I used my military ICW bag, and a fleece sleeping bag liner.

No moisture was obvious anywhere in the system either night/morning. The first night there was a ton of moisture buildup on both the inside and outside of my tarp (it was FOGGY!!!), but nothing inside my hammock or bags.

I stayed toasty warm both nights. Weasel was out with me in his HHSS, but I'm not sure what he used for top insulation.

I can't imagine that there is a breathable SB out there...although tyvek has been considred a "breathable vapor barrier".

And the only way I can imagine trying to actually test what works best would be to spend time in one setup, break down and reset for the other condition, and then spend the same time in the new setup...assuming the rest of the test conditions remain consistent throughout your test period.

I can't vouch for much other than again I used the HHSS, with SB, this past weekend in weather down around 30 deg and pretty humid out both nights. Inside the hammock I used my military ICW bag, and a fleece sleeping bag liner.

No moisture was obvious anywhere in the system either night/morning. The first night there was a ton of moisture buildup on both the inside and outside of my tarp (it was FOGGY!!!), but nothing inside my hammock or bags.

I stayed toasty warm both nights. Weasel was out with me in his HHSS, but I'm not sure what he used for top insulation.

30 and foggy and warm and dry? With the old SB again? So, how you gonna beat that?

For I consider that the sufferings of this present time are not worthy to be compared with the glory that is to be revealed to us....that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. For we know that the whole creation groans and suffers the pains of childbirth together until now.
Romans 8:18,21-22

I went camping in the mountains (tail end of smokeys) in October and the low was in the 40s. I simply suspended a space blanket beneath my HH and slept in my sleeping bag. I had the hex tarp over me. There was a very small amount of condensation right in the bottom of the SB. I thought of making a few pin holes right there. I was so warm I sweated.

Last month I put my new HHSS on my hammock and camped down into the low 30s. Just the HHSS with the pad - no space blanket. In my sleeping bag and was comfy cozy too. There was no condensation. I also had the hex tarp over me.